Screw cutting device for automatic lathes



@ww m S Q May 19, 1931.' o. scHAERER E1' AL I SCREW CUTTING DEVICE FOR AUTOMATIC LATHES Filed Aug. 2, 192s IWI.

Patented May 19, 1931 vUNITED STATES PATENT ol-rlclsA g OTTO SCHAERER AND FRITZ POPPENSIEKER, 'OF COLOGNE, GERMANY, ASSIGNORS TO Y THE FIRM .ALFRED`H. SCI-IUTTE, OF COLOGNE-DEUTZ, GERMANY SCREW CUTTING DEVICE FOR .AUTOMATIC LATI-IES Application filed August 2, 1929, Serial N'o. 382,865, and in Germany May 24928.l

of the threaded mandrel must be reversed periodically so that energy losses are involved in the necessary braking and accelerating operations.

Also screw cutting devices on multi-spindle automatic lathes are known in which the tool is pressed against the blank for the purpose of starting the cut whereas the traverse for cutting the thread is effected by the threads of the tool and blank which are in engagement. The disadvantage of this device is that the sides of the thread on the blank have to take up the axial pull.

The present invention avoids these disadvantages. It consists in that the threaded mandrel rotates unidirectionally in a rotary mandrel guide and is caused to screw out of and into said guide by being driven alternately at a speed smaller than or greater than the speed of rotation of the mandrel guide.

One embodiment of the invention is repsented by way of example in Fig. l. Fig. 2 shows a detail on a larger scale. The tool spindle 27 carrying the tool 28 is mounted so as to be rotatably and axially displaceable in the tool slide 29, and is driven from the shaft 28 with which it is connected by the connecting sleeve 25 so as to be readily disengageable. The mandrel 26 is arranged on the shaft 23 between the collar 24 and the connecting sleeve 25 and is prevented from rotating relatively to the latter by means of a tongue and groove. The mandrel screws out of and into the mandrel guide 18 in a manner to be described subsequently'and in so doing causes the forward and backward motion of the tool 28. In contradistinction to the known devices the mandrel guide 18 also rotates and the mandrel 26 is screwed into and out of the latter, without alteration of the sense of rotation by being driven alternately at a speed smaller than or greater- The drive of the mandrel 26 andthe mandrel guide 18 is effected together with that of the blank 6 in the following manner. p The blank carrying spindle 5 carrying the blank 6 is driven from the main shaft 1 by means of the gearing 2, 8, 4. The intermediate shaft 9 is driven from the main shaft 1 by means ofthe gear wheels 7, 8 and from this intermediate shaft the mandrel guide 18 is driven by means of the gearing 10, 12 and the rotation of the mandrel 26 is derived either from the gearing 8, 14 or byY gearing 11, 13. The transmission ratio may, for example, be so chosen that the mandrel guide 18 rotates in the same direction and at the same speed as the blank 6 whereas the mandrel 26 is driven by means of the gearing 11, Y13 at a lower speed of rotation than the mandrel guide 18, or on the other hand by the gearing 8, 14 at a higher speed of rotation, so that the mandrel screws out of guide respectively. Thus on the forward traverse the tool 28 has a speed of rotation smaller than that of the blank 6 but in the saine direction and consequently cuts a thread in the blank. 28 still rotates in the same direction as the blank 6 but with a higher velocityand consequently makes the return motion. In the embodiment described the pitch of the thread of the mandrel 26 is equal to that of the thread to be cut. It can, however, be different by employing a different transmission ratio. A

If a left handed thread is to be cut instead of a right handed one, then the tool passes on to the blank at the higher speed and is withdrawn from it atthe lower speed.

The connection between the gear wheel 12 and theA mandrel guide 18 is effected by means of a sleeve 15 connected with the gear wheel 12 by a pin 16, the pin 16, Fig. 2, engaging in a slot of the collar 17 on the mandrel guide 18 so that this latter rotates with the gear wheel 12. The mandrel guide 18 is held y against axial motion in the sleeve l5 by the or into the f On the return motion the tool -v ico of the mandrel 26 connected thereto with thev transmission gearing 11, 13 on the one hand and 8, 1li-on 1fthe other, .is effected by means of the coupling sleeve 22 which is axially dis `laceable on 'a hollow shaft`21 in `which the sha' t 23 in turn is guided by means Iof a tongue and gro-ove so as to be axially displaceable. In its left and right hand end ,positions the coupling sleeve 22 'engages in the hubs formed as couplings ofthe gear wheels .13 and 14 respectively :so that yt-he shaft '23 and the mandrel 26 are gi-ven a smaller speed lof rotation than the mandrel guide '18 in the left hand end position of he coupling sleevel 22 and a higher speed in the right Ahand end position r'of the lsleeve 22 Yand in consequence screw out of and into ythe 'mandreljguide 18,5the tool 28 cuttingathread in the blank 6 and 'being again withdrawn therefrom. In the-central position of the sleeve 22 in which itis not connected with the hub of either 'wheel the shaft 23 will be rotated at'the same'speed as the mandrel .guide 18 'in consequence `of kthe 'friction 'in 'the threads 'so that in 'this position 4of the coupling vsleeve a forward or Ibackward -motion of the too'l spindle 2T does notoc'cur.

The :screw cutting arrangement -is automatically reversed `in the following manner: The rods 30, 31, 32 engage in the connecting sleeve 25 vand A'transmitthe axial motion of the tool spindle '27, which in 'the :case of cutting the thread 'is towards 'the "left, to a release member journalledin guides 34 and provided 'with .a"'wedgeshaped trip '33.. In its forw ardmo tion the wedge-shaped oblique surface ofthe release member `33engages the spring controlled =pawl 35 and raisesthesa-me. In consequence the swinging *lever 36 is released and the coupling sleeve 22,shown in its left hand end position, brought the action of the spring 37 and the levers 33 39 to the right hand end positi'onand thus into engagement with the gear :14 so that the 1tool l28 is lagain -withdrawn from 'the pre- 'viously cut thread.` rIhe 4lengthof'thetlnead 'to be cut-can be adjusted by'setting'the :arm 32 and the Vrelease member 33` connected therewith.

.In order to return the coupling sleeve '22 from Ithe right hand end position tothe central and lto the left handend position a controlling disc ,412 is provided which :is `driven correspondingly slowly from 'the control shaft 43 of the machine by means of a mono# toothed coupling 45. This control disc is provided with two preferably adjustable projections 40, 41 of different heights which in turn contact with the lower end of the swinging :arm 36l and thus bring the lattea- ;and at the same time the coupling sleeve 22 irst int-o the central and then into the left hand end position, the pivotedlever 36 being vheld lin position by means of the two notches on the pawl 35. Before vthe coupling sleeve 22 v'passes from the middle position to the left hand end position (advance of the tool) the blank 6 .must :be :exchanged for a .fresh one, a certain time being required for this operation. 'During this period the lcont/rol discs L12 operating l'the swinging lever 36 must 1remain stationary which 'for example may be 'effected in that the cont/rol lshaft rotating periodically vrin either direction is connected Vwifththe control 'disc42 by means of a monotooth coupling 15 in vsuch manner that the control disc 212 is yonly :driven Vwhen the control shaft lrotates in 4the lone vdirection and remains stationary when the control shaft rotates in A'the opposite direction. rlhe projecti'ons Ll() and 111 are arranged onthecontrol -disc y'212 in such manner -that Ethe control idisc t2 comes to rest when the projection 40, but not thegproject-ion 41, has already :engaged with lthe swinging "lever 36. rIo ensurethis intermediate position a springropera'ted pauil i421 is provided which #engages in a correspending `recess -lor notch 2161onitheicam fdisc 1. A screw Vcutting device for automatic lathes comprising a itool 'mounted 'for rrotative and axial movements, a unid-ire'c'tionally -rotated mandrel for reecting the forward 1andloaclrward motion of said tool, a mandrel guide rotating lin `the same direction as the mandrel and -threadedly engaged therewith, and mechanism for driving-said mandrel a'lternately at higher-and lower -speeds v'than the speed of rotation of ysaid guide, substantially 'asset forth.

2. ,In an automatic `lathe .adapted for screw cutting, in combination, a mandrel, a manv drel guide drivenfat constant speed in 'thread- :ed engagement with lthe mandrel, 'two gear .trains adapted to drive said mandrel at different speeds, and a .coupling member Aaxially .displaceable for engaging saidlmandrel with either of vsaid gear trains, substantially .as -set :for-th.

f3. In Van `automatic -lathe for cutting screws, in combination, la blanlr rotating unidire'ctiona'lly aat-:constant speed, a tool mount- `edffor rotative and Vaxial movements, a mandrel for reciprocating said to-ol, la 'rotary lguide Ydriven at constant `'speed in threaded ement with-the Xmandrel, and means for rotatingsaidomandrel alternately faster and slower relatively to the speed of said guide, substantially as set forth.

4. In an automatic lathe for cutting screws, in combination, a` tool mounted for rotative and axial movements, a rotating mandrel for reciprocating said tool, a rotating guide for and engaging with said mandrel, two gear trains for driving said mandrel, a sliding sleeve for coupling either of said gear trains with said mandrel, and cam-operated springopposed lever mechanism for displacing said sleeve, substantially as set forth.

5. In an automatic lathe for cutting screws, in combination, a tool mounted for rotative and axial movements, a rotating mandrel for reciprocating said tool, a rotating guide for and engaging with said mandrel two gear trains for driving said mandrel, a sliding sleeve operatively engaging either of said gear trains with said mandrel, means for displacing said sleeve and means for lockin said sleeve in its position, substantially as set forth.

6. In an automatic screw cutting lathe, in combination, a unidirectionally rotated mandrel guide, a unidirectionally rotated mandrel threadedly engaging with said guide, two gear trains for driving said mandrel at diderent speeds, coupling mechanism for engaging said mandrel with either of said gear trains, and means comprising a cam disc driven from the lathe for operating said coupling mechanism, substantially as set forth.

7 In an automatic screw cutting lathe, a mandrel guide rotated in one direction and a mandrel rotated in the same direction and threadedly engaged with said guide, substantially as and for the purpose set forth.

8. Automatic screw cutting machine, comprising in combination, a mandrel guide rotated at constant speed and a mandrel rotated in the same direction and connected with said guide for rotative and axial movement relative thereto, and mechanism for imparting motion to said mandrel substantially as described and illustrated in the accompanying drawings.,

In testimony whereof we have signed our names to this specification.

OTTO SCHAERER. FRITZ POPPENSIEKER. 

